Treatment of mineral sand for the separation of one constituent therein from another



Patented June I 1937 TREATMENT or sarm'non mm SAND non m. or one cons'rrrmm'r THEREIN FROM ANOTHER 4 Miles Andrew Corbett, London, man's No Drawing. Application August 2, i983, Serial I This invention relates to the treatment of mineral sands, and more particularly to the treatment of beach sands, for the separation of one constituent therein from another. The inven- 5 tion for example provides an improved process for the recovery of zircon contained in beach sands in association with quartz, rutile, monazite, ilmenite, garnet and other silicates.

This type of sand occurs on beaches in various parts of the world, notably in Brazil, Travancore, and Florida. The sands are usually treated by removing the magnetite, ilmenite and monazite by any suitable type of magnetic separator and then treating the non-magnetic portion, which contains the zircon, rutile, and a little monazite and garnet, by gravity concentration .methods on shaking or air tables. This treatment of non-magnetic sands is not only tedious, but gives a relatively poor recovery of m product which usually contains from one to three per cent of rutile and from two to seven per cent of monazite. To obtain a pure zircon sand from this product it has hitherto been a necessary to resort to chemical treatment involving a relatively costly series of operations.

It has previously been proposed to separate various silicate and other non-metallic minerals from one another by various flotation processes so involving the use of soaps and fatty acids with or without the addition of other reagents but to the best of my knowledge none of these processes has been adapted to the treatment of such relatively coarse and complex mineral mixtures 85 as beach sands nor to the separation of zircon from monazite, rutile, garnet and the like. It

is an object of the present invention to provide a satisfactory commercial method for the separation of zircon from the minerals with which it is associated in beach sands. The invention can be applied to the sand as found on the beach without crushing but is preferably applied to such sand after the magnetic portion (containing the flmenite and/or magnetite) and the lighter quartz have been removed so as to obtain an enrichment of the sand in zircon.

According to the present invention one constituent of a mineral sand is separated from another by a flotation process. The term lie- 50 tation process" is intended to cover both true flotation in which the particles of one constituent are made to float upon the surface of the liquid present and also what is more accurately referred to as a gravity process wherein the 55 particles of one constituent are made to rise zircon resulting in a comparatively low-grade Great Britain August 1:,

above those of another constituent without necessarily rising to the surface of the liquid.

In a preferred process, after .a preliminary separation of the magnetic portion of the sand from the non-magnetic portion by subjecting the sand to treatment by any known or suitable type of magnetic separator, and preferably after removing the quartz on shaking tables or the like, the zircon particles are, in accordance with the present invention, separated from the remaining particles of the non-magnetic portion of the beach sand by agitating the sand with a very dilute soap solution together with a frothing oil. The oil may be of the essential oil type or a tarry oil or even a higher alcohol provided that the frothing oil is definitely soluble, but only to a small extent, in the soap solution. Suitable oils comprise pine oil, eucalyptus oil, cresol or the like. The soap used may be any of those found in commerce, such for example as sodium oleate, sodium palmitate or sodium steara'te or the corresponding potassium compound or the alkali. salts of sulphonated derivatives of unsaturated alcohols.

As the result of a selective action of the soap upon the particles ofsand, a fllm of oil forms around only the zircon particles. The agitation of the sand in the oily soap solution is carried out under such conditions that the air which is thereby introduced into the mixture, is split up into minute bubbles. These bubbles,v attach themselves to the oiled zircon particles and cause them to rise to the surface as a froth or scum, the air bubbles apparently having substantially no aflinity for the unoiled particles of sand. This froth need not necessarily float on the surface of the water so long as it rises above the heavy particles of unoiled sand, so that by passing the treated sand over shaking tables the zircon particles, which have'been rendered relatively light by the attachment of air bubbles, are readily washed away from the heavier unoiled particles of the sand.

Obviously a combination of true flotationv (in which the zircon particles actually float to the surface of the liquid) and the above described gravity process may be used to separate the zircon particles from the other particles of sand. A jigging process is also satisfactory for this I have also found that the addition of a thicker oil or fat such, for example, as oleic acid, olein or similar unsaturated fatty acids or glycerides or sulphonated derivatives thereof, phenol, cresol and the'like, or their sulphonated deriva- I'br example, in the case of acidic substances ployed, or even the frothing oil itself may be used as solvent. For example, oleic acid or cresol may be disposed in dilute ammonia, caustic soda or ethyl or butyl alcohol.

,To assist in preventing the oiling of the rutile, garnet, monazite and other impurities in the nonmagnetic portion of the beach sand, I may add to the oily soap solution a small quantity of an alkaline reagent which may comprise ammonia or an alkali hydroxide or a compound of an alkali metal with a weak acid which gives a solution with a hydrogen ion concentration greater than 1 17.

oiling or flotation of the monazite may also be prevented by treating the sand with a dilute solution of an acid, such, for example, as hydrochloric acid, prior to treatment in the oily soap solution. In neutral or slightly alkaline solutions the monazite tends to float with the zircon and obviously this acid treatment can be applied to the monazite-zircon fraction obtained in the first flotation so as to cause the monazite to sink when the zircon is again floated to obtain a purer zircon product.

The presence in the water of soluble salts of metals which give insoluble soaps tends to improve the flotation of the zircon, but is not necessary to cause flotation, and in all cases an excess of suchsalts should be avoided, as there is a tendency for the other minerals to oil when such an excess is present.

With some varieties of beach sand the zircon may be oiled or floated without the use of soap if olein, oleic acid. or other fatty or tarry oil is used in conjunction with a frothing agent, but the best extractions are usually obtained when soap is present.

In order that this invention may be more fully understood the following examples of methods of carrying it into efl'ect are given although the invention is not restricted to these examples. In

all cases the examples refer to sand obtained from a. beach sand by first removing the ilmenite and most of the monazite by a magnetic separa-' tion and then washing away the quartz on shaking tables. The product so obtained may consist of approximately 68% of zircon, 25% of rutile, 2% of monazite and 5% of silicate minerals other than zircon, such as sillimannite, cyanite, garnet.

Example 1 10 kilograms of the sand are agitated in a rotating cylinder, containing baiiles or riiiles but no grinding devices, with 5 litres of water containing 0.5 gram of sodium oleate, 2 grams of sodium hydroxide and about 0.5 cc. of pine oil. After 10 minutes oleic acid is added drop by drop with constant rotation of the mixture until the zircon collects into flocculent masses through which the rutile, etc. settles to the bottom when the cylinder is brought to rest. The mixture is then passed over a small shaking table across which a slowcurrent of water is passed perpendicular to the set of the riilies; the flocculated zircon is thereby washed away and the rutile colcentrate launder of the table.

lected in the riflles and shaken towards the con- One, or at the most two, retreatments of the rutile concentrate are usuallyv sufllcient to free it from zircon while a second passage of the zircon over the tables sufllces to remove practically all adherent rutile.

I The final products obtained may be (A) 6150 grams of a zircon fraction containing 98% zircon, about 1.5% monazite and about 0.5% rutile, (B) 814 grams of an intermediate fraction, containing 52% zircon, 40% rutile and 5% monazite,-and (C) 3020 grams of a rutile product containing 72% rutile, 8% zircon and 4% monazite.

Example 2 10 kilograms of the same sand are agitated with 10 litres of 0.1% caustic soda solution in a sub-aeration flotation machine run at a slow speed and suflicient pine oil is added to give a copious froth. Alternate additions of a 0.05% solution of sodium oleylsulphonate (a commercial sulphonated soap) and of a 2% solution of oleic acid in caustic soda are made until the zircon begins, to accumulate in the froth; as each lot of mineralized froth is drawn off from the top of the water, further quantities of soap and oleic acid are added through the air. intake pipe to cause more zlrconto float; When the froth begins to show signs of rutile accumulating with the zircon, the receiver is changed and flotation continued until a relatively clean rutile is obtained; the middling product obtained in this way is returned to the machine and treated again with more of the original sand. The rutile product which falls to float in the recovery of the middling product may assay rutile, 7% zircon, 3% monazite and 10% miscellaneous minerals: the zircon obtained in the first froths may assay 97.5% zircon, 1% rutile and 1.5% monazite and represents a recovery of 82% of the zircon in the sand.

Treatment of the zircon sand concentrates obtained as described in either of the above examples with 20% hydrochloric-acid and reflotation of the washed sand may yield products containing over 99% zircon, since the monazite and most of the rutile fail to float after the acid said concentrate from the monazite contentthereof.

2. A process for the treatment of mineral sands for the recovery of zircon therefrom which comprises the step of agitating said sand with air in a dilute soap solution containing oil which has at least a constituent which is soluble to a small extent in said soap solution, said oil in-- cluding a fatty oil, and separating the zircon from other constituents by a flotation process.

3. A process for the treatment of mineral sands for the recovery of zircon therefrom which comprises the step of agitating said sand with air in a dilute soap solution containing a fatty oil in quantity suflicient to cause flocculation of the airaoaasss con particles and a frothing oil to cause the air to break up into fine bubbles which attach themselves to said fiocculated zircon particles.

4. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the steps of agitating said zircon-containing sand with air in a dilute soap solution containing an oil which is soluble to a small extent in said soap solution, and separating the said aggregates from the nonzircon minerals by a flotation method.

5. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the steps of agitating said zircon-containing sand with air in a dilute soap solution containing an oil which is soluble. to a small extent in the said soap solution to cause the zircon particles to form flocculated aggregates the specific gravity of which is less than that of the other minerals of the sand by reason of the included air bubbles, and. separating the said lighter aggregates from the non-zircon minerals by a gravity flotation method.

6. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the steps of agitating said zircon-containing sandwith air in a dilute solution containing an oil which is soluble to a small extent in the said soap solution to cause the zircon particles to form flocculated aggregates the specific gravity of which is less than that of the other minerals of the sand by reason of the included air bubbles, and separating the said aggregates from the non-zircon minerals by a method selected from a group consisting of jigging, and passage over shaking tables.

'I. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the steps of agitating said zircon-containing sand with air in a dilute soap solution containing an oil which is soluble to a small extent in said soap solution, whereby flocculation of the zircon particles is produced, and separating the flocculated zircon particles from the said sand by a froth flotation process.

v 8. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the step of agitating said zircon-containing sand with air in a dilute soap solution containing an oil which is soluble to a small extent in sai'if'soap solution, said solution being maintained in a slightly alkaline condition, whereby flocculation of the zircon particles is produced, and separating the flocculated zircon particles from the said sand by a froth flotation process.

9. A process for the treatment of zircon-containing mineral sands for the recovery of zircon therefrom which comprises the steps of washing said sand in a dilute acid and thereafter agitating said sand with air' in a dilute soap "solution containing an oil-which is soluble to a small extent in said soap solution, whereby flocculation of the zircon particles is produced, and separating the flocculated zircon particles irom the said sand by a froth flotation process.

10. A process for the treatment! of zircon-containing mineral sands for the recovery or zircon therefrom which comprises the step of agitating said zircon-containing sand with air in a dilute soap solution containing an oil whlchis soluble .to a small extent in said soap solution, said soap being obtained by combining oleic acid with an alkali and said solution being maintained in a slightly alkaline condition, whereby flocculation of the zircon particles is produced, and separating the flocculated zircon particles from the said sand by a froth flotation process.

11. A process for the treatment of zircon-containing mineral sands for the recovery of'zircon' therefrom which comprises the step of agitating said zircon-containing sand with air in a dilute soap solution containing an oil which is soluble to a small extent .in said soap solution, said oil being introduced in solution in an alcohol into said soap solution, whereby flocculation of the zircon particles is produced, and separating the flocculated zircon particles from the said sand by a froth flotation process. 

